1. Field of the Invention
The present invention relates in general to a sail system for wind turbines of the vertical shaft type designed to convert wind energy into electrical energy and, more particularly, to a structural improvement in a sail system for the vertical shaft type wind turbines including a plurality of plate sails rotatably mounted to a support frame.
2. Description of the Prior Art
As well known to those skilled in the art, typical wind turbines are generally classified into two types, that is, the wind turbines of the horizontal and vertical shaft types. The vertical shaft type wind turbines are operated by the force of wind against sails rotating about a vertical rotating shaft, thereby converting wind energy into electrical energy. FIG. 4 is a perspective view showing the construction of a typical sail system for vertical type wind turbines. As shown in the drawing, a plate sail 1 is rotatably mounted to a support arm 2 of a support frame. When the arm 2 of the above sail system is placed at a position where the arm 2 may rotate in the direction R.sub.1 opposite to wind direction W', the sail 1 is turned to the direction R.sub.2, which is the same as wind direction W', relative to the arm 2. The sail 1 in the above state will not resist the wind force. The above sail system thus rotates more easily thereby increasing the rotating force of the wind turbines.
In the above sail system, the sail 1 is pivoted to the tip 2a of the arm 2 at its side 1a by means of a hinge 3, thereby being selectively turned about the arm's tip 2a. That is, the sail 1 pivoted to the arm's tip 2a leans to the outward direction. The sail 1 thus causes the hinge 3 to easily break due to the sail's weight. The sail 1 also easily sags from the arm 2. As the side 1a of the sail 1 is pivoted to the arm's tip 2a by the hinge 3, the side 1a must have a configuration which allows the side 1a to be parallel to the tip 2a and thereby is suitable to be pivoted to the tip 2a. Another problem of the above sail system resides in that the system has a spring 4 which connects the side portion of the sail 1 to the arm's tip 2a so as to prevent the sail 1 from turning exceedingly relative to the arm's tip 2a.